One type of container which is well known comprises an outer relatively rigid plastic layer and an inner relatively flexible inner layer. The outer layer is provided with an atmospheric vent opening such that the inner flexible layer collapses and delaminates from the outer layer when the liquid contents are dispensed. In the manufacture of such containers, it is common to apply a differential pressure to insure that the delamination will occur. In addition, it is usually necessary to trim the containers. Typical containers are shown, for example, in U.S. Pat. Nos. 5,435,452 and 5,513,761. Such containers are used with dispensers such as pump dispensers or spray dispensers and the inner layer, sometimes called a bag, is made of a resin which is compatible with the liquid contents.
Among the objectives of the invention are to provide a multilayer container wherein the container does not require trimming and the like; wherein the atmospheric vent opening is obtained during the blow molding of the package; wherein any tendency of the inner layer to adhere to the outer layer is eliminated; and wherein no delamination step is required in the manufacture.
In accordance with the invention, the multilayer container comprises an outer relatively rigid plastic layer having a body portion, a finish defining an opening and a base. The outer rigid layer has an atmospheric vent opening therethrough. The container includes an inner flexible plastic layer of relative thin flexible material throughout which does not adhere to the outer plastic layer. The inner flexible layer has a closed bottom portion engaging the inner surface of the finish of the outer plastic layer and a radially extending flange portion of the inner layer overlying the finish of the outer layer. The outer layer preferably comprises an olefin and the inner layer preferably comprises amorphous nylon. The method of making the multilayer container includes coextruding a parison comprising a relatively thick outer layer of plastic material and a relatively thin inner layer of plastic material, the outer plastic material and inner plastic material being such that the layers will not adhere to one another, closing molds about the parison, blow molding the parison to form an outer rigid plastic layer having a body portion, a finish defining an opening, and a base and an inner flexible layer of relatively thin flexible material throughout which does not adhere to the outer plastic layer and the inner flexible layer having a portion engaging the inner surface of the finish of the outer plastic layer and a radially extending flange portion of the inner layer overlying the finish, and simultaneously forming an atmospheric vent opening to the outer layer. During the blow molding, the base of the outer layer is formed with an outer generally planar surface and a diametral slit. A portion of the inner layer extends along the inner surface of the base of the outer layer and a portion of the inner layer extends into the opening but not beyond the outer surface of the base. When the contents are dispensed by a differential pressure, air enters through the vent opening and the inner layer readily delaminates from the outer layer without the need of any prelamination step in the making of the container.